Suggestions:
When user enters the date effective from which the price is applicable. If this is specified it is treated as an addition condition to the price. This becomes more relevant for ‘List’ type price list. However, when the user enters the valid upto, it is the date up to which the price list is valid. System considers the pricelist start date as the date effective from and pricelist ends on the date valid upto considering that start date cannot be end date for a pricelist.